Plug terminal



SPt 8, 1959 G. c. slTz 2,903,670

PLUG TERMINAL l Filed March 24, 1954 INVENTR. Gilbert C. Scz

United States PLUG TERMINAL Gilbert C. Sitz, Paxtonia, Pa., assignor to Incorporated This invention relates in general to plug contact assemblies and more particularly to plug conductor terminals of the snap-in lock type.

In the conventional type of snap-in lock plug terminals, a metallic pin contact element, usually formed by machining or casting is secured to the end of a lead conductor and inserted and retained in a plug receiving receptacle by means of a wire spring detent and cooperating recess arrangement. Commonly, the recess takes the form of an annular groove on the pin element with the detent being a wire spring mounted in the sidewalls of the receptacle, although the reverse arrangement wherein the spring detent consists of a wire insert within the contact pin is also utilized. In either case the inclusion of a Wire spring in the plug contact assembly has 'several disadvantages, among these being that the wire detent is particularly subject to distortion through accidental mishandling or abuse, yor through acquisition of a permanent set due -to continued use. Obviously, setting of the spring from its original character would impair or perhaps destroy its effectiveness to hold the plug terminal in place.

Plug terminals in the conventional form are generally restricted to metallic construction which obviously requires that the plug receptacle be of electrical insulating material even though a metallic structure may be preferred as where strength is a design factor. In addition, the conventional plug terminal has the further disadvantage of not being wholly insertable in the receptacle, the exposed portion including the point at which the lead conductor is axed to the terminal. In order to protect the plug terminal from short-circuiting and from break- `age at the point of connection, it has been the practice in many instances to provide for the assembly some form of covering, usually being either a separate covering element placed over the assembly after connection, or a molded insulation surrounding the exposed portion of the plug terminal, which adds to the diiculty and expense of manufacture.

It is, therefore, an object of the present invention to provide an improved plug terminal which is effective, yet simple and inexpensive to produce by automatic means.

Another object of Ithe present invention is to provide a plug terminal having an improved snap-in lock arrangement in which the taking of a permanent set is immaterial.

A further object of the present invention is to provide a plug terminal in which the electrical connection between the lead wire and terminal is inherently protected by the arrangement of the plug elements.

Still another object is to provide a plug terminal adapted for use with plug receptacles of any material of construction.

An additional objective resides in the provision of a commercially feasible organization which will be substantially foolproof in use and which overcomes certain well-known disadvantages inherent in the prior art.

arent O rfice Other important features and objects of the invention .tto which reference has not been made hereinabove will appear hereinafter when the following description and claims are considered with the accompanying drawings.

In this specication and the accompanying drawings I have shownk and described a preferred embodiment of my invention, but it is to be understood that such embodiment is not intended to be exhaustive nor limiting of the invention but, on the contrary, is given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify and adapt it in various forms, each as may be best suited to the conditions of a particular use.

Figure l is a fragmentary view in cross section of a typical form of plug receptacle for the purpose of illus- `trating the manner in which the plug terminal may be mounted therein;

Figure 2 is a fragmentary plan view of the plug recep-tacle; and

Figure 3 is a view in cross section of the plug terminal.

In order to illustrate the objectives of the present invention it will be described in connection with one particular form the cooperating plug and receptacle may take. It is to be understood, however, that the invention may be adapted to other forms of plugs and receptacles according to the applications and purposes for which the plug assembly is designed. Referring to Figure l, generally designated at `ll is a plug receptacle in which a plug terminal, generally `designated at 3, is inser-ted and thereby to be retained in electrical contact with a cooperating contact element, not shown, that may be an integral part of receptacle l or external thereto, the form of such contact element being immaterial. While the contact portion of plug terminal 3 may take any convenient form, for purposes of illustration, however, plug 3 includes a pin contact nose 5 extending beyond the rear side of receptacle Il whereby to engage with an external contact element which may be of the form shown and described in my copending application, S.N. 411,969, filed February 23, 1954. Receptacle 1 may be of any suitable material, either electrical conducting or nonconduoting, and typically is provided with a plug receiving aperture 2 into which projects a keeper or detent 4 that serves to retain plug terminal 3 in the receptacle in a manner to be described. Detent 4, in the embodiment disclosed, is simply formed by providing a lip on the rear face of the receptacle which extends over a small segment of aperture 2 as shown in Figure 2.

In the preferred embodiment of the invention plug 3 gener-ally includes a pin contact body 6 of any suitable conducting material, which is mounted in a sleeve 8 of insulating material, such as nylon or other suitable plastic material having sufficient resilience and exibility. It is contemplated that insulating sleeve S should substantially enclose pin Contact body 6 whereby upon insertion into the aperture 2 the engagement areas of receptacle 1 and plug 3 will be between sleeve S and the side Walls of aperture 2, the conductive Contact body 6 being fully insulated from receptacle I. Contact body 6, however, may be of sufficient length, as at pin 5, to project from the insertion end of sleeve 8 a sulicient distance to provide an external contact surface for the plug.

While sleeve 8 may be directly molded over contact body 6, it is preferred that the elements be separately formed to facilitate automatic manufacture, sleeve 8 being separately molded and Contact body 6 being stamped from sheet metal stock and rolled into tubular form as shown in Figure 3. To maintain the elements assembled a shank seciton 10 of contact body 6 is enlarged in diam-l eter to provide a shoulder 11 which cooperates with an annular stop shoulder l2 within sleeve 8 and serves to limit the insertion of contact body 6 within the sleeve. Enlarged shank section l@ is provided with a flared end 14 which, by virtue of having a larger diameter than an internal annular bead 15 in the end of sleeve 8, snaps into a cooperating groove lo, after distending the end of sleeve 8 at bead l5, concomitant with shoulder 1l abutting shoulder l2. Bead l5, after contraction behind flared end i4, serves to retain contact body 6 within sleeve 8.

A stop shoulder i7 formed by enlarging the end section 18 of sleeve 8 defines the limit of insertion of the plug into aperture 2 by engaging the face of receptacle 1. The plug is retained in the receptacle by means of an annular groove 2t) in the in insertion end of the sleeve 6, groove Z0 providing a recess for seating detent 4 coincident with shoulder 17 engaging the face of receptacle 1. lt is contemplated, of course, that detent 4 shall extend sufliciently far into aperture 2 so as to prevent free passage of the plug therethrough. Hence, to permit groove 2% to be moved into cooperative relationship with detent 4, the forward end of sleeve 8 is relieved from contact body 6, as by enlarging at 2l the inner diameter thereof, whereby as the plug is inserted into the receptacle, sleeve 8 may yield under pressure from detent 4. After detent 4 seats in groove 20, the forward end of sleeve 8 snaps back into its original shape thereby to maintain the plug in position.

The forward edge of sleeve 8 may be inclined to form a ramp or camming surface Z2 to guide more efficiently detent 4 to groove 20.

As best shown in Figure 3, the plug 3 constitutes the terminal of an electrical lead 23 which may be secured to contact body 6 by any suitable means. It is preferred, however, that the diameters of the insulated portion 24 and the stripped portion 25 of lead 23 be substantially the same as the diameters of enlarged shank 10 and nose 5, respectively, of contact body 6 which may thus be suitably crimped or swaged to lead 23, as by indentations 26, within that poriton of plug 3 which is received in recep-tacle l. As thus connected, when the plug is mounted in the receptacle the points at which contact body 6 are secured to lead 23 are within the body of the receptacle, and hence, are fully protected from external shock.

It will be evident that improved means are provided whereby the failure of a plug of the snap-in type due to setting or distortion of the snap member is minimized. Moreover, it is to be noted that even should the yieldable forward end of sleeve S become slightly distorted, no impairment of the locking function thereof results since the forward end of sleeve 8, including ramp 22, is forced to conform to the desired shape in order to reenter aperture 2 during withdrawal of the plug from the receptacle.

In a typical application embodying the invention the multiple receptacle will take the form of a molded panel provided with apertures 2 and will be relatively rigid and unyielding. Sleeve S, of nylon or other suitable material, will be accurately molded to an external diameter itting within the interior surface defined by an aperture 2. The inner surfaces within sleeve 3 will make a nice force iit with shank section l0 of the metal plug. Thus the nose of the plug will be cushioned coaxially, with the axis of aperture 2. The parts may, therefore, be mass produced and yet each nose, when the assembly is complete, will be held by the nylon sleeve exactly where it should be with respect to its cooperating contact spring.

An advantage inherent in the present assembly arises from the fact that the nylon possesses some natural resilience so that a bending force applied to the end of the nose of the plug can move the plug slightly, within the yieldability of the nylon, to bring the axis of the nose to a slight angle with respect to the axis of the aperture and in this manner the nose may accommodate itself to a contact spring bearing up-o-n the nose with greater than normal pressure. Similarly the nose can yield under a blow, or through other unintended forces applied to it and so avoid taking a permanent set. Forces beyond a certain amount, however, will bring the shaft of the nose in the region Z7 into engagement with the nylon molding at its left hand end, as viewed in Figure 3, at the opening into the enlarged portion of diameter 21. This enlarged diameter 21 serves, therefore, not only to provide the desired relief for detent 4 but also to inject a region of clearance for limited yielding movement of nose 5 when the plug is positioned in an aperture 2. The nylon skirt at 2l backs up the shaft of the nose, however, when excessive force is applied to it and provides a rm reinforcement against further disalignment of the metal conductor within the dielectric sleeve.

Changes in construciton will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective against the prior art.

I claim:

l. A plug terminal for insertion in a plug receiving receptacle having a detent projecting therein comprising a contact member, a resilient sleeve fitted on said member, a recess in said sleeve for cooperating with the detent to retain said terminal in the receptacle, the forward end of said sleeve from said recess being spatially disposed and longitudinally fixed relative to said member for yieldably impeding movement of said recess into and out of coop eration with the detent for yieldably securing said terminal in the receptacle.

2. A plug terminal for insertion in a plug receiving receptacle having a detent projecting therein comprising a contact pin, a resilient sleeve fitted on said pin, the insertion end of said sleeve being relieved from and longitudinally xed relative to Said pin and having an inclined edge, an annular groove in said end adjacent said inclined edge for cooperating with the detent to maintain said terminal in the receptacle, said inclined edge engaging and snapping under the detent upon the seating of the detent in said groove during insertion of said terminal in the receptacle.

3. A plug terminal `for insertion into a plug receiving receptacle having a detent projecting therein comprising a contact member, a resilient sleeve fitted on said member, a first portion of said sleeve having an enlarged internal diameter to define inwardly opposed stop shoulders at the ends thereof, said contact member including an enlarged sleeve retaining portion for snapping within said sleeve and into engagement with said stop shoulders, a second portion of said sleeve being yieldably disposed relative to said member, a recess in said second portion for cooperating with the detent to maintain said terminal in the receptacle, said second portion snapping under the detent to bring said recess into cooperation with the detent upon insertion of said terminal in the receptacle.

4. A plug terminal for insertion in a plug receiving receptacle having a detent projecting therein comprising a tubular contact member including a pin contact portion and an enlarged shank portion having a flared end, said portions forming a stop shoulder at the junction therebetween, a resilient insulating sleeve having first and second opposed internal annular shoulders for cooperating with said stop shoulder and said flared end respectively to retain said sleeve on said member, the inside diameter of said sleeve at said second shoulder being less than the diameter of said flared end so that upon assembly of said sleeve on said member said iirst shoulder abuts said stop shoulder as said flared end snaps under and into engagement with said second shoulder, the forward end of said sleeve being yieldably dispose-d relative to said member, an annular groove in said forward end for cooperating with the detent to maintain said terminal in the receptacle, said forward end being arranged to snap under the detent upon the seating thereof in said groove when said terminal is inserted in the receptacle.

5. A plug terminal for insertion in a plug receiving receptacle having a detent projecting therein comprising a contact member, a resilient sleeve secured on said member, the forward end portion of said sleeve being yieldably disposed relative to said member and constrained to Hex primarily about axes of flexure parallel to the longitudinal axis of said plug terminal, the end of said sleeve being inclined to p-rovide an annular ramp engaged by the detent upon insertion of said terminal into the receptacle, the external diameter of said sleeve behind said ramp being reduced for receiving the detent upon forcing said ramp past the detent, said sleeve having lateral means on said sleeve for stopping insertion of the terminal within the receptacle upon movement of said ramp past said detent.

6. In combination, a body member having a passageway therein, a plug disposed in said passageway including a contact element and a resilient member secured on said element, the forward end of said resilient member defining a ramp and being reduced in section immediately behind said ramp to define a shoulder, said forward end being spatially disposed relative to said contact element, a detent projecting from said body member and intersecting said passageway and cooperating with said shoulder for impeding movement of said plug thereby, the plug periphery at the high point of said ramp closely matching the conguration of said passageway for Aconstraining said resilient member to flex abofut axes of ilexure parallel to the longitudinal aXis of said plug upon the ramp passing under said detent.

References Cited in the le of this patent UNITED STATES PATENTS 2,142,818 Jacobson Jan. 3, 1939 2,205,146 Larkin June 18, 1940 2,330,948 Brand Oct. 5, 1943 2,383,909 Buchanan Aug. 28, 1945 2,469,397 Mezek May 10, 1949 2,689,337 Burtt Sept. 14, 1954 2,694,798 Cole Nov. 16, 1954 2,695,394 Watts Nov. 23, 1954 2,711,522 Goodwin June 21, 1955 2,774,810 Ritter Dec. 18, 1956 

